The present invention is directed to electronic article security and tracking systems which use resonant security/tracking tags.
Electronic article security (EAS) systems for tracking as well as detecting and preventing theft or unauthorized removal of articles or goods from retail establishments and/or other facilities have become widespread. In general, such security systems employ a security tag which is secured to or associated with an article (or its packaging). Such an article is typically readily accessible to potential customers or facility users and, therefore, is susceptible to unauthorized removal. Security tags may take on many different sizes, shapes and forms depending upon the particular type of EAS system in use, the type and size of the article to be protected, the packaging for the article, etc. In general, such EAS systems are employed for detecting the presence (or the absence) of a security tag and, thus, a protected article within a surveilled security area or detection zone. With respect to use for preventing theft, in most cases, the detection zone is located at or around an exit or entrance to the facility or a portion of the facility.
With respect to tracking, for example, articles of clothing available for sale in a retail establishment, it may be desirable to track the physical location of such articles of clothing within the establishment. For example, it may be desirable to track when each individual article of clothing is removed from a fixture, such as a metal clothing rack, to obtain data to be used, for example, for manufacturing additional quantities of articles of clothing that receive the most customer attention based on data related to removal of such articles from the fixture.
However, the use of conventional radio frequency identification (RFID) technology to track articles of clothing in retail environments is difficult due, in part, to the display fixturing used for the clothing. Metal clothing racks or fixtures tend to interfere with antennas placed in walls or ceilings near clothing being displayed. Further, the movement of clothing on rolling racks or fixtures presents a challenge in the placement of antennae for article tracking. As the need increases to track garments within a retail space, rather than tracking garments just at store exits, placement of antennae is increasingly difficult.
One type of EAS system which has gained widespread popularity utilizes a security tag which includes a self-contained, passive resonant circuit in the form of a small, generally planar printed circuit which resonates at a predetermined detection frequency within a detection frequency range. A transmitter, which is also tuned to the detection frequency, is employed for transmitting electromagnetic energy into the detection zone. A receiver, tuned to the detection frequency, is positioned proximate to the detection zone. When an article having an attached security tag moves into or passes through the detection zone, the security tag is exposed to the transmitted energy, resulting in the resonant circuit of the tag resonating to provide an output signal detectable by the receiver. The detection of such an output signal by the receiver indicates the presence of an article with a security tag within the detection zone.
Recently, passive resonant security tags which return unique or semi-unique identification codes were developed. U.S. Pat. No. 5,446,447 (Carney et al.), U.S. Pat. No. 5,430,441 (Bickley et al.), and U.S. Pat. No. 5,347,263 (Carroll et al.) disclose three examples of such security tags. These security tags typically include an integrated circuit to generate the identification code. Such “intelligent” security tags provide additional information about the article detected in the zone of the interrogator.
It would be desirable to use such passive resonant security tags or even active resonant security tags which return unique or semi-unique identification codes in an article tracking system where there is minimal interference from metal clothing racks or fixtures and where antenna placement difficulties due to movement of rolling racks or fixtures are minimized.
All references cited herein are incorporated herein by reference in their entireties.